1. Field of the Invention
The present invention relates to an apparatus and a method for detecting and delineating cancerous lesions, and more particularly an apparatus and a method for effective and affordable early detection of cancerous lesions using gamma rays or other radiation to obtain image data.
2. Description of the Related Art
As medical therapies become more biochemically specific, medical researchers and practitioners have turned to molecular imaging to develop new therapies and guide treatment with these therapies. Positron emission tomography (“PET”) is the archetypal molecular imaging device, due to its high sensitivity to extremely small amounts of biochemically-relevant molecular probes. With such small amounts (e.g., tracer quantities), it is possible to monitor biochemical processes without substantially altering enzymatic kinetic rates.
The detection of early primary cancers with whole-body PET has been less successful than the detection of metastatic activity. This performance difference has been ascribed to instrumental limitations, as well as biological differences between primary cancers as compared to metastases. In general, it is preferable to detect primary cancers when they are small, since the chances of cure and control are substantially increased. The small size of early cancer reduces lesion detectability because of the finite resolution of the PET device, which effectively reduces lesion-to-background contrast. In the PET field, reduced lesion-to-background contrast can be quantitatively measured with the recovery coefficient. This effect has been extensively explored in phantom and clinical trials by Dr. Lee Adler. For example, see “Simultaneous Recovery of Size and Radioactivity Concentration of Small Spheroids with PET Data”, C. Chen, L. Adler et al., J. Nucl. Med. 40(1), 1999, pp. 118–130; and “A Non-Linear Spatially Variant Object-Dependent System Model for Prediction and Correction of Partial Volume Effect in PET”, C. Chen, L. Adler et al., IEEE Trans. Med. Imag. 17:214–227, 1998.
In U.S. patent application Ser. No. 09/737,119, Publication No. 20010040219, Cherry et al. disclose a detector for use in a dedicated PET scanner for cancer applications, particularly breast cancer applications, using at least two detector plates containing arrays of LSO or light-equivalent scintillating crystals and a fiber-optic bundle serving as a light-guide between the scintillator arrays and photomultiplier tubes. However, in the Cherry system, a fiber-optic bundle must be placed in at least two detector plates. In addition, in the Cherry system, the fiber-optic light guides are attached to the scintillator arrays and to the photomultipliers permanently, and these attachments are fixed and not removable. Such a fixed and non-removable arrangement may lead to practical difficulties when, for example, a medical intervention using data provided by the system requires physical access that may be obstructed by the fibers, or when the scintillator arrays and/or fiber optics are contaminated by body fluids so as to require disposal or sterilization. Thus, there is a need for a more flexible PET scanner system that allows the optical fibers to be removable from a photomultiplier or scintillator.